Pretty much what u/MySweetUsername linked to, but you need to make sure you get the one that's specific to your vacuum model and is built to take the kinds of rechargeable battery that you have. Like for me I have a V8 Dyson and DeWalt Batteries, so I had to get one according to those specs. I think it's like 2 or 3 screws to take the old Dyson rechargeable battery out, and then the battery adapter attaches using those same screwpoints and screws. You can't use the original Dyson charger or hanging dock now, so when the battery dies you have to take the battery off the vacuum and put it on it's OEM charging station (and even without the battery the vacuum still won't hang on the wall mount), but it's a small extra step to greatly extend the life of an otherwise great vacuum.